This is related to RAM based systems. During upgrade process some packages installed previously but missing in new cache may not be installed after first reboot of upgraded system. Consequently after changes have been committed with out noticing of missing packages /etc/apk/world will be rewritten and list of packages will be cut. Perhaps we need some algorithm to force update from new repositories before first reboot after upgrade.

(from redmine: issue id 616, created on 2011-04-28, closed on 2011-10-06)